Hydroalkylation of aromatic hydrocarbons

ABSTRACT

Hydroalkylation of aromatic hydrocarbons is effected under controlled temperature conditions in the presence of a volatilizing liquid diluent to yield product hydroalkylate containing decreased quantities of undesired by-products.

United States Patent Suggitt HYDROALKYLATION OF AROMATIC HYDROCARBONS 3,347 945 10/1967 Siaugh .r260/668F [75] Inventor: Robert M. Suggitt, Wappingers Primary Examiner c Davis Fans Attorney, Agent, or Firm-T. H. Whaley; C. G. Ries [73] Assignee: Texaco Inc., New York, NY.

[22] Filed: May 7, 1973 [21 Appi. No.1 358,217 [571 ABSTRACT Hydroalkylation of aromatic hydrocarbons is effected [52] US. Cl. 260/668 R, 260/667 der omrolled temperature conditions in the presr ence of a volatilizing diluent to product I held f March 260/667, 668 668 F hydroaikylate containing decreased quantities of undesired by-products. [56] References Cited UNITED STATES PATENTS 18 Claims, 1 Drawing Figure 3,153,678 /1964 Logemann 260/667 A c 99 6d 5/ 91 94 if 54 f 75 77 74 ?6 PATENTED FEB 1 5 1 1 Q m w \m a v. @Q Q Q 1 7 %Q \m Q Q N Q A J mm W% 1 \m% \m\ mm MN mm 1 W 1+. & w? \x A Q. 5 a Q Q 1 W 7 \w m Q @C Q Q Q Q Q a Q my w Q r m% 1 R3 4 1 K Kw w w HYDROALKYLATION OF AROMATIC HYDROCARBONS BACKGROUND OF THE INVENTION This invention relates to hydroalkylation. More par- 5 ticularly it relates to the controlled hydroalkylation of benzene to yield product hydroalkylate containing decreased quantities of undesired by-products.

As is well known to those skilled in the art, it is possible to hydroalkylate aromatic. preferably mononuclear, hydrocarbons such as benzene. toluene, etc. by reaction with hydrogen at hydroalkylation conditions to yield product hydroalkylate. The latter typically contians, in the case of the hydroalkylation of benzene, the desired cyclohexylbenzene together with unreacted hydrogen and benzene and by-products such as (a) naphthenes including methylcyclopentane, (b) cyclohexylbenzene impurities, i.e., impurities boiling within the boiling range of cyclohexylbenzene and which therefore are difficultly separable, (c) dicyclohexylbenzenes including the preferred para-isomer and the less preferred non-para-isomers, and (d) heavier by-products such as tricyclohexylbenzenes.

It is apparent that economic recovery of desired cyclohexylbenzene is facilitated if hydroalkylation is carried out in manner (a) to control formation of byproducts, i.e., to decrease their formation to the lowest level possible and (b) to control their formation, consistent with the first requisite, to permit attainment of more preferred by-products at the expense of less preferred by-products.

It has now been found that hydroalkylation, as heretofore carried out, is highly dependent on the temperature at which the reaction is carried out (undesirable by-products being produced when the temperature is not controlled and particularly when it is permitted to increase) and more particularly that a non-uniform temperature gradient across the catalyst bed conduces the formation of undesirable by-products. It does not appear to be readily possible to effectively control the temperature of reaction by limiting the supply of one or both of the reactants because this substantially affects the makeup of the product. Heat exchange does not appear to be useful because of the fact that the reaction is carried out within a few inches of the catalyst bed.

It is an object of this invention to provide a process for hydroalkylation. It. is another object of this invention to provide a process for hydroalkylation under controlled conditions. Other objects will be apparent to those skilled in the art.

STATEMENT OF THE INVENTION In accordance with certain of its aspects, the novel process of this invention for hydroalkylating a charge mononuclear hydrocarbon with a hydroalkylating quantity of hydrogen may comprise passing said charge hydrocarbon, said hydroalkylating quantity of hydrogen, and an inert diluent in liquid phase, through a hydroalkylation operation at hydroalkylating conditions in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge hydrocrabon and forming a product stream containing hydroalkylate;

volatilizing said inert diluent into said product stream during said hydoralkylation thereby absorbing at least a portion of the exothermic heat of hydroalkylation; and

recovering said product stream containing hydroalkylate.

DESCRIPTION OF THE INVENTION The charge mononuclear aromatic hydrocarbons which may be hydroalkylated by the process of this invention may include benzenes, including substituted benzenes, such as benzene se. toluene, xylenes, etc. The preferred charge may be benzene se.

Hydroalkylation may preferably be effected in one embodiment by passing to the hydroalkylation operation a charge mononuclear aromatic hydrocarbon, typically benzene, together with recycled materials, typically dicyclohexylbenzenes. Among the latter may be ortho-dicyclohexylbenzene, meta-dicyclohexylbenzene, and para'dicyclohexylbenzene.

The charge which may be hydroalkylated by the process of this invention may include, in addition to fresh charge benzene, other components including cyclohexylbenzene, para-dicyclohexylbenzene, tricyclohexylbenzenes, etc. The composition of the charge (ex hydrogen) entering the reactor may include:

Other components may be present, including methyl cyclopentyl benzenes, bicyclohexyl, tricyclohexyl benzenes, etc.

Preferable 100 parts by weight of benzene and ahydroalkylating quantity, preferably 0.2-10 parts, more preferably 0.3-5 parts, say 2.5 parts by weight of hydrogen may be employed for hydroalkylation.

Hydroalkylation may be effected in the presence of a hydroalkylation catalyst and a hydroalkylating quantity of hydrogen. The hydrogen need not be pure; but preferably hydrogen of %l00% purity may be used. The hydrogen should preferably be free of any impurities which may poison the catalyst. Hydrogen recov ered from a reforming operation may be suitable.

The catalyst may contain a Group VIII transition metal component, e.g., cobalt, nickel, ruthenium, rhodium, palladium, iridum, and platinum. The preferred type of catalyst may include a Group VIII metal, typically nickel or cobalt; and it may also contain 0-30%, typically l0%20%, say 19% ofa Group Vl metal, typically tungsten, on a silica-alumina catalyst support. When the Group VIII metal is Co or Ni, it will preferably be present in an amount of 2%-30%, typically 4.0%-25%, sayv 22%. When the Group VIII metal is a noble metal, it may be present in amount ofO.2%-5%, say 1%. Such a catalyst may be prepared for example by impregnating or ion-exchanging a commercial NI-I exchanged Y zeolite catalyst with, e.g., nickel nitrate (or cobalt nitrate) and thereafter wtih ammonium metatungstate solution and then drying the catalyst in air at say 100C. The so-dried catalyst may be mixed with an amorphous silica-alumina support further dried at 150C, and then calcined to a maximum temperature up to 800C.

The catalyst may be calcined during which residual nitrates are decomposed and the catalyst is dehydrated. The catalyst may (preferably after loading into the hydroalkylation unit) be reduced in the presence of hydrogen for a minimum of I hour and typically at least 4-8 hours at a temperature preferably above about 300C. and typically 300C.700C., say 500C.

The so-prepared typical catalyst may contain, on a dry basis, 6% nickel, 19% tungsten, and 22% bydrogen-Y zeolite, the remainder being amorphous silica-alumina support.

Hydroalkylation of aromatic feed may be effected by using this catalyst at an LHSV of l.0-15, typically 2-10, say 3.

The pressure of hydroalkylation may typically be lOO-l ,500 psig, preferably 100-500 psig, say 500 psig; at this pressure the reactants are maintained substantially in liquid phase except for the hydrogen which is in gas phase.

It is a feature of the novel process of this invention that hydroalkylation be carried out in the presence of an inert liquid diluent which may he volatilized during hydroalkylation thereby absorbing at least a portion of the exothermic heat of hydroalkylation. The inert liquid diluent may preferably be one which is in liquid phase at the conditions prevailing at the inlet to the hydroalkylation operation eg temperature of 25C-220C, typically of 80C-200C, at pressure of I1,500 psig.

The preferred inert liquid diluent may be one which may vaporize to a significant degree (typically at least about 30%) at the conditions prevailing in the hydroalkylation operation typically at a temperature of lC-2I0C at l00l,500 psig. In the preferred embodiment the inert liquid will have a bubble point or boiling point within the hydroalkylation range and typically at the temperature and pressure at which the operation is to be carried out. Where several liquids fulfill this requisite, it is normally desirable to utilize that with the highest latent heat of vaporization.

Clearly the inert liquid diluent should be one which is non-reactive with the other reactants or with the catalyst under the conditions of operation; and it is preferred that the diluent be free of catalyst poisons such as sulfur, oxygen, etc.

In the preferred embodiment, the inert liquid diluent should not possess physical properties (e.g., boiling point) which may interfere with the facile recovery and purification of materials leaving the hydroalkylation operation-particularly the charge aromatic hydrocarbon, commonly benzene, and the principal product, commonly cyclohexylbenzene.

Although it may be possible to utilize, as the inert liquid diluent, a liquid having a narrow boiling range such as an LNG or a naphtha, it is preferred to use one having a fixed composition. The preferred liquids include lower paraffin and naphthenic hydrocarbons. It may be found desirable to use those which have an atmospheric boiling point which is 20C-80C, preferably C-70C, say about C below that of the'charge hydrocarbon to be hydroalkylated. The inert diluent liquid will preferably have a boiling point higher than the boiling point of the charge mononuclear hydrocarbon.

When the charge hydrocarbon to be hydroalkylated is benzene, the preferred diluent may have a boiling point of about 10C to 130C, preferably 20C-IO0C, say about 35C. Typical inert diluents may include npentane (b.p. 362C), isopentane (28C), n-heptane (984C), cyclopentane (495C), 2,2-dimethylbutane (49.7C), methylcyclopentane (718C), etc. Preferred is n-pentane or n-heptane.

When the charge hydrocarbon to be hydroalkylated is toluene, the preferred diluent may have a boiling point of about 30C-l 30C, preferably 60C-85C, say about 80C. Typical inert diluents may include cyclohexane (b.p. 8l.4C). any of the five dimethylcyclopentanes (878C to 995C), n-hexane (69C), ethylcyclopentane (b.p. l03.5C), n-heptane (984C), noctane (l25.6C) etc. Preferred are C; to C hydrocarbons, including cyclohexane or n-heptane.

In the preferred embodiment, the inert liquid diluent may be present in the typical charge mixture of the above table in amount of 5200 parts, more preferably l0-60 parts, say 25 parts.

In practice of the process of this invention the charge, including the inert liquid diluent, may be passed to hydroalkylation at 25C23()C. preferably 8()C-200C, and IOU-1,500 psig. As hydroalkylation occurs in the catalyst bed at LHSV of 0.5-l 5, typically 2-6, say 2, (basis the aromatic feed) the temperature of the reaction mixture may rise to l25C-2l0C at l00-l ,500 psig. When the temperature of the reaction mixture rises the inert liquid diluent will volatilize; and the reaction mixture will be maintained at a lower temperature so long as inert diluent is still present in liquid phase. The heat liberated by hydroalkylation of eg the benzene may be absorbed by the volatilizing eg npentane; and hydroalkylation is effected with lower temperature rises across the catalyst bed. Although it may be possible to operate at nearly isothermal conditions over most of the course of the reaction, in practice it may be found that the increase in temperature may be maintained at 0%-98%, preferably 30%-90%, say of the temperature increase attained in prior practice.

Reaction is typically carried out to permit volatilization of more than 10%, preferably 30%l00%, say about of the inert diluent during the course of hydroalkylation. Although it may be possible to operate the reactor with removal of the volatilized diluent directly from the reactor during the course of reaction, it may be preferred to pass the reactor effluent to a separation zone in which volatilized inert diluent may be separated.

It will be apparent that the inert liquid diluent may be added to the reaction mixture prior to initial temperature conditioning preceding admitting to the reaction operation after initial temperature conditioning just prior to admission to the reaction operation, or during the reaction operation se. In the preferred embodiment, inert diluent liquid may be admitted with the charge to be hydroalkylated.

' Hydroalkylation may be carried out in two or more stages; and when this is the case, the volatilizing diluent may be added between stages.

The composition of hydroalkylate product will be a function of the charge to the hydroalkylation operation. In one embodiment where the charge is parts 5 of benzene, 0.3-5 parts, say 2.5 parts by weight hydrogen, and 10-200 parts, say 25 parts of n-pentane inert diluent liquid. the product (ex hydrogen) may typically contain the following in liquid phase:

10 %-l preferably 50%- 75%, say 60 of the inert diluent, eg n-pentane, may be found in the gas phase (depending on the temperature and pressure) together with any hydrogen which is in the product mix.

The separated hydroalkylate, free of hydrogen and containing some inert diluent, may be passed to an inert liquid diluent recovery operation wherein typically the inert diluent is recovered as by distillation, and returned to be used eg as make-up to be mixed with the charge to hydroalkylation. Preferably the bottoms, free ofinert diluent may be subjected to further distillation to separate unreacted charge benzene as overhead this typically being recycled to charge benzene.

The benzene-free hydroalkylate may be further distilled to separtae as overhead desired product eg cyclohexylbenzene and, as bottoms, a stream containing heavier components including dicyclohexyl benzenes and tricyclohexyl benzenes.

The process of this invention may typically be carried out as set forth in detail in the process flow sheet in the accompanying drawing.

Charge benzene to be hydroalkylating may be admitted in amount of 30-150 parts, say 47 parts through line 10 together with 0-60 parts, say 53 parts of recycled benzene in line 11 and 0.3- parts, say 2.5 parts of hydrogen in line 12. The total charge stream in line 13 may be mixed with -200 parts, say 25 parts of npentane from manifold 14. Although it may be desirable to admit n-pentane through one or more of lines 15, 16, 17, l8, l9 and 20, it is preferred that admission be through line 15 (5-100 parts, say 10 parts) and line 18 (5-100 parts, say 15 parts).

The total charge mixture in line 13 may be at 70150C, say 100C and l00-l,500psig, say 500 psig which is sufficient to maintain the mixture mostly in liquid phase except for the hydrogen which is in gas phase. If necessary the charge mixture may be cooled in cooler 21 prior to passage to hydroalkylation operation 22. Contained therein is a bed of catalyst particles 8% cobalt dispersed on a rare-earth exchange Y- type zeolite in a silica-alumina matrix.

Reactor effluent in line 23, at l25C-250C, say 200C and 100-1 ,500 psig, say 500 psig, includes typically about 24 parts of n-pentane in the vapor phase and about 1 part of n-pentane in the liquid phase. This effluent in line 23 is passed to separator 24 wherein pentane in vapor phase is recovered through line 25 and passed to manifold 26. Effluent in line 27 contains hydroalkylate from vessel 24 including pentane in liquid phase in amount of say 1 part.

When hydroalkylation is carried out in two stages, as in the process of the flowsheet shown in the drawing, it may be desirable to hydroalkylate in the first stage at 400-1 ,500 psig say 800 psig and in the second stage at a lower pressure, -1 ,000 psig, say 500 psig. In this instance, the drum 24 may be a flash drum rather than a separation drum; and the liquid may be cooled during flashing.

It is a feature of the process of this invention that hydroalkylation be carried out in hydroalkylation operation 22 to yield desired cyclohexylbenzene in amount of 5-20 parts, say 15 parts with a temperature increase of only 10C-100C, say 50C.

1n this embodiment, the liquid in line 27 may contain the following:

0.3-5, say 2.5 parts of hydrogen are added through line 28 to the stream in line 27; and 0-100 parts, say 15 parts of n-pentane (liquid) are admitted through line 18. The mixture at say C is cooled in exchanger 29 to say 100C and passed to hydroalkylation operation 30 which preferably contains the same catalyst as does hydroalkylation operation 22.

Effluent in line 31 is at 120C-200C, say C, the temperature increase in operation 30 being 20C-100C, say 60C. This stream, containing say 24 parts of n-pentane in vapor phase and say 1 part of npentane in liquid phase is passed to separation operation 32 wherein the vaporized n-pentane is withdrawn through line 33 into manifold 26. n-pentane in manifold 26 is passed to cooler-condenser 34 wherein it is condensed. Hydrogen gas, if present, may be withdrawn through lines 35 and 36 and/or optionally recycled through line 37 where itjoins with fresh charge hydrogen admitted from manifold 28 through line 38 and thence through line 12 to line 10.

n-pentane, condensed in exchanger 34, is collected in vessel 39. Pentane may be admitted thereto through line 40 or withdrawn therefrom through line 41.

The net hydroalkylate in vessel 32, withdrawn through line 42 contains the following:

line 67 has the following composition:

Liquid in line 42 is preferably passed through heat exchanger 43 wherein it is heated and passed to diluent separation operation 44 from which, in this embodiment, overhead is recovered through line 45, condensed in condenser 46, and collected in vessel 47. Liquid in line 48 includes pumped reflux returned to tower 47 through line 49. Net product withdrawn through line 50 includes say 1 part of n-pentane, and contains less than about 1 part of other components. A portion of this stream may be withdrawn through line 51, the major portion being recycled through line 52 to vessel 39.

Bottoms from tower 44 may be reboiled in reboiler circuit 53, 54, and 55; the net bottom withdrawn through line 56 may be of the following composition:

cyclohexane The stream in line 56, is passed through heat exchanger 57 and then to benzene separation operation 58. Overhead is withdrawn through line 59, condensed in condenser 60, and collected in vessel 61. Condensate in line 62 includes 30-87 parts, say 40 parts of benzene, 0.2-2.5 parts, say 0.5 parts of methylcyclopentane, and 1-15 parts, say 8 parts of cyclohexane. One portion is passed as pumped reflux through line 63 to tower 58; and the remainder is recycled through line 11 to charge line after methylcyclopentane and cyclohexane removal (not shown).

Bottoms in tower 58 are reboiled in reboiler circuit 64, 65, and 66 and withdrawn through line 67 in amount of 123-74 parts, say 53 parts. The liquid in TABLE Component Typical Preferred cyclohexylbenzenc l0-35 25 cyclohexylbenzene impurities 1 02-4 0.5

dicyelohcxylbenzenes 2-30 25 dicyclohexylbenzene impurities 0.l-2 0.5

tricyclohexylbenzenes 0-5 2 The cyclohexylbenzene mixture in line 67 is heated in exchanger 68 and passed to cyclohexylbenzene recovery operation 69.

Overhead, withdrawn through line 70, is condensed in exchanger 71 and collected in vessel 72. A portion is passed through line 73 as pumped reflux; and say 25.5 parts are withdrawn through line 74 as cyclohexylbenzene of purity greater than Bottoms in tower 69 are reboiled in reboiler circuit 75, 76, and 77 and withdrawn in amount of say 27.5 parts. Bottoms withdrawn through line 78 contain dicyclohexyl benzenes and higher boiling components as follows:

TABLE Component Typical Preferred dicyclohexylbenzenes 2-30 25 dicyclohexylbenzene impurities 0.l-2 0.5 tricyclohexylbenzenes 0-5 2 DESCRlPTION OF PREFERRED EMBODIMENTS Practice of the process of this invention may be apparent to those skilled in the art from inspection of the following examples wherein, as elsewhere in this specification. all parts are parts by weight unless otherwise specified.

EXA MPLES l-lX In practice of the process of this invention according to one embodiment, hydroalkylation is effected by use of a catalyst which is prepared from a support of a zeolite X (containing 84 aluminum atoms per unit cell) which was exchanged with ammonium ion and thereafter with rare earth' (lanthanum, cerium, and neodymium). The rare earth exchanged zeolite was mixed with four'times its weight of silica-alumina and then on this composite was deposited 8% cobalt. The mass was pelleted, calcined for 3 hours at 800C, and then prereduced at 538C for 2 hours in hydrogen flowing at 300 v/v per hour at atmospheric pressure.

During hydroalkylation, benzene, in liquid phase, is admitted to the reactor together with the hydroalkylating quantity of hydrogen. In control Examples 1 and 11, benzene was the only hydrocarbon charge admitted at a WHSV of 2. In experimental Examples 111 and IV, the benzene was replaced by an equal weight of a mixture of4 parts by volume of benzene and 1 part by volples 111 and IV. the para-isomer is formed in amount of 87% and 97% of the metaisomer; in control Examples I and 11, the corresponding values are 77% and 79.5%. Thus is obtained an improvement averaging about 18%.

Results comparable to those achieved, e.g., in experi? mental Examples llllv may be achieved by use of the following liquid diluents:

ume of n-pentane. Hydroalkylation is carried out at op- 10 EX mu] M a 1 C l U eratmg pressure of 500 psig (partial pressure of hydro q gen). V n-heptane The product is collected and analyzed. The following Vi i bl f h h f h Vll Z-Z-drmethylhutane ta e sets ort t e composition, In terms wetg tperm methylcyclopentane cent, of the product hydroalkylate (free of hydrogen). 15 Experimental Examples Ill and IV are tabulated as analyzed and also as recalculated on a pentane-free basis. The hydroalkylation oftoluene to produce methylcy- TABLE Process Conditions I ll lll IV Inlet Temp C 126 137 I30 135 Max Temp of Bed C 219 214 204 199 Product Analysis n-pcntanc 190-1 20.13 methylcyclopentane 1.71 1.45 0K9 111 0.80 1.00 cyclohcxanc 6.00 5.13 6.2-1 7.77 6 2 791 hcn/cnc 51.47 56 ll 41 )l 2 l' J2 l0 5} 71 cyclohcxylhcn/unc impurities 1.23 1.01 0110 0 7 0 51 0.06 cyclohexylbenzene 26.83 24.101 17.46 21 74 10 4 X4 dicyclohcxylhenzenc impurities 0.66 0.45 0.41 0.51 0.35 0.44 m-dicyclohexylhcnzene 5.51 5.51 5.93 7.3K .19 6.25 p-dicyclohexylhenzenes 4.25 4.39 5.11% 6.45 .22 6.54 tricyclohcxyl henzenes 0.67 0.79 1.43 1.78 1.41 1.76 Heavier 0.59 0.32 0.30 0.37 0.30 0.38

From the above Table, it will be apparent that practice of the process of this invention permits attainment of desirable, improved results. The average increase in bed temperature of control Examples I and II is 85C while the average increase in bed temperature of experimental Examples 111 and 1V is 69C a desirable decrease of 19%.

The amount of cyclohexylbenzene impurities (i.e., impurities boiling in the cyclohexylbenzene boiling range of 230 C- 240C) as a percentage of the desired cyclohexylbenzene is substantially decreased to 3.5% (Example Ill) and 3.15% (Example lV) qv 4.6% (in control Example 1) and 4.16% (in control Example 11). This represents a decrease of these undesired components averaging about 22.5%.

It will also be apparent that practice of the novel process of this invention desirably decreases the formation of by-product naphthenes (as methylcyclopentane) in terms of by-product cyclohexane. Experimental Examples Ill and 1V yield methylcyclopentane in amount of 14.3% and 12.6% cf control Examples H] with 27.1% and 27.3%. Thus the formation of undesirable methylcyclopentane is reduced by about 50%.

The process of this invention also permits hydroalkylation under conditions which permit the desired product cyclohexylbenzene to be produced with simultaneous production of substantially increased quantities of desirable by-product para-dicyclohexylbenzene and decreased quantities of undesired non-para (principally meta-) dicyclohexylbenzene. In experimental Exam- Example Liquid 1X cyclohexane X dimethylcyclopentanes X1 n-hexane Xll n-heptane Although this invention has been illustrated by reference to specific embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made which clearly fall within the scope ot this invention.

I claim:

1. The process for hydroalkylating a charge mononuclear hydrocarbon with a hydroalkylating quantity of hydrogen which comprises passing said charge hydrocarbon, said hydroalkylating quantity of hydrogen, and an inert diluent in liquid phase, through a hydroalkylation operation at hydroalkylating conditions in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge hydrocarbon and forming a product stream containing hydroalkylate; withdrawing said product stream-containing said hydroalkylate from said hydroalkylation operation;

passing said withdrawn product stream to a separation operation;

forming in said separation operation (i) a vapor containing said volatilized inert diluent and (ii) a cooled product stream;

withdrawing from said separation operation (i) said vapor containing said volatilized inert diluent and (ii) said cooled product stream; and

recovering said product stream containing hydroalkylate.

2. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent in liquid phase possesses a boiling point different from the boiling point of hydroalkylate.

3. The process for hydroalkylating a charge mononuclear hydrocabon as claimed in claim 1 wherein said inert diluent possesses a boiling point lower than the boiling point of said hydroalkylate.

4. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent possesses a boiling point lower than the boiling point of said charge mononuclear hydrocarbon.

5. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent possesses a boiling point higher than the boiling point of the charge mononuclear hydrocarbon.

6. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is a C to C hydrocarbon.

7. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is selected from the group consisting of n-heptane, n-pentane, iso-pentane, noctane, methyl cyclopentane, and 2,2-dimethylbutane.

8. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is volatilized, during said hydroalkylation, in amount sufficient to maintain said hydroalkylation operation within a predetermined temperature range.

9. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene in liquid phase, said bydroalkylating quantity of hydrogen, and an inert liquid diluent through a hydroalkylation operation at hydroalkylating conditions including inlet temperature of C230C in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge benzene and forming a product stream containing hydroalkylate including cyclohexylbenzene; withdrawing said product stream containing said bydroalkylate from said hydroalkylation operation; passing said withdrawn product stream to a separation operation;

forming in said separation operation (i) a vapor containing said volatilized inert diluent and (ii) a cooled product stream;

withdrawing from said separation operation (i) said vapor containing said volatilized inert diluent and (ii) said cooled product stream; and

recovering said product stream containing said hydroalkylate.

10. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is selected from the group consisting of n-heptane. npentane, iso-pentane, methyl cyclopentane, and 2.2- dimethylbutane.

11. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is pentane.

12. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is separated from said product stream containing hy droalkylate.

13. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert diluent is volatilized during said hydroalkylation in amount of at least about 30%.

14. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert diluent is volatilized substantially completely during said hydroalkylation.

15. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene in liquid phase and said hydroalkylating quantity of hydrogen through a hydroalkylating operation at inlet temperature of 25C-230C and -1 ,500 psig in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge hydrocarbon and forming a product stream containing hydroalkylate;

withdrawing said product stream containing said hydroalkylate; recovering hydroalkylate uct stream;

admitting to said product stream prior to withdrawal from said hydroalkylating operation an inert diluent in liquid phase selected from the group consisting of n-heptane, n-pentane, iso-pentane, n-octane, methyl cyclopentane, and 2,2-dimethylbutane whereby at least a portion of said inert diluent volatilizes thereby abosrbing at least a portion of the exothermic heat of hydroalkylation;

and forms (i) a vapor containing said volatilized inert diluent and (ii) cooled product stream; and withdrawing said vapor containing said volatilized inert diluent.

16. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene, hydrogen, and an inert diluent in liquid phase through a first hydroalkylating operation at inlet temperature within the hydroalkylation temperature range of 25C230C and at hydroalkylation pressure in the presence of hydroalkylation catalyst thereby forming a partially hydroalkylated product stream;

flashing said partially hydroalkylated product stream to a pressure lower than that prevailing at the outlet of said first hydroalkylation operation thereby volatilizing at least a portion of said inert diluent and cooling said partially hydroalkylated product stream to a temperature below that prevailing at the outlet of said first hydroalkylation operation; passing said cooled partially hydroalkylated product stream and hydrogen to a second hydroalkylation operation at inlet temperature within the hyfrom said withdrawn proddroalkylation operation is less than the pressure in said first hydroalkylation operation.

18 The process for hydroalkylating a charge'benzene with a hydroalkylating quantity of hydrogen as claimed in claim 16 wherein the pressure in said second hydroalkylation operation is equal to the pressure to which said partially hydroalkylated product stream is flashed upon exiting said first hydroalkylation operai :0: i in 

1. THE PROCESS FOR HYDROALKYLATING A CHARGE MONONUCLEAR HYDROCARBON WITH A HYDROALKYLATING QUANTITY OF HYDROGEN WHICH COMPRISES PASSING SAID CHARGE HYDROCARBON, SAID HYDROALKYLATING QUANTITY OF HYDROGEN, AND AN INERT DILUENT IN LIQUID PHASE, THROUGH A HYDROALKYLATION OPERATION AT HYDROALKYLATING CONDITIONS IN THE PRESENCE OF HYDROALKYLATION CATALYST THEREBY EXOTHERMICALLY HYDROALKYLATING SAID CHARGE HYDROCARBON AND FORMING A PRODUCT STREAM CONTAINING HY DROALKYLATE; WITHDRAWING SAID PRODUCT STREAM CONTAINING SAID HYDROALKYLATE FROM SAID HYDROALKYLATION OPERATION; PASSING SAID WITHDRAWN PRODUCT STREAM TO A SEPARATION OPERATION; FORMING IN SAID SEPARATION OPERATION (I) A VAPOR CONTAINING SAID VOLATILIZED INERT DILUENT AND (II) A COOLED PRODUCT STREAM
 2. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent in liquid phase possesses a boiling point different from the boiling point of hydroalkylate.
 3. The process for hydroalkylating a charge mononuclear hydrocabon as claimed in claim 1 Wherein said inert diluent possesses a boiling point lower than the boiling point of said hydroalkylate.
 4. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent possesses a boiling point lower than the boiling point of said charge mononuclear hydrocarbon.
 5. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent possesses a boiling point higher than the boiling point of the charge mononuclear hydrocarbon.
 6. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is a C5 to C8 hydrocarbon.
 7. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is selected from the group consisting of n-heptane, n-pentane, iso-pentane, n-octane, methyl cyclopentane, and 2,2-dimethylbutane.
 8. The process for hydroalkylating a charge mononuclear hydrocarbon as claimed in claim 1 wherein said inert diluent is volatilized, during said hydroalkylation, in amount sufficient to maintain said hydroalkylation operation within a predetermined temperature range.
 9. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene in liquid phase, said hydroalkylating quantity of hydrogen, and an inert liquid diluent through a hydroalkylation operation at hydroalkylating conditions including inlet temperature of 25*C-220*C in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge benzene and forming a product stream containing hydroalkylate including cyclohexylbenzene; withdrawing said product stream containing said hydroalkylate from said hydroalkylation operation; passing said withdrawn product stream to a separation operation; forming in said separation operation (i) a vapor containing said volatilized inert diluent and (ii) a cooled product stream; withdrawing from said separation operation (i) said vapor containing said volatilized inert diluent and (ii) said cooled product stream; and recovering said product stream containing said hydroalkylate.
 10. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is selected from the group consisting of n-heptane, n-pentane, iso-pentane, methyl cyclopentane, and 2,2-dimethylbutane.
 11. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is pentane.
 12. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert liquid diluent is separated from said product stream containing hydroalkylate.
 13. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert diluent is volatilized during said hydroalkylation in amount of at least about 30%.
 14. The process for hydroalkylating a charge benzene as claimed in claim 9 wherein said inert diluent is volatilized substantially completely during said hydroalkylation.
 15. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene in liquid phase and said hydroalkylating quantity of hydrogen through a hydroalkylating operation at inlet temperature of 25*C-230*C and 100-1,500 psig in the presence of hydroalkylation catalyst thereby exothermically hydroalkylating said charge hydrocarbon and forming a product stream containing hydroalkylate; withdrawing said product stream containing said hydroalkylate; recovering hydroalkylate from said withdrawn product stream; admitting to said product stream prior to withdrawal from said hydroalkylating operation an inert diluent in liquid phase selected from the group consisting of n-heptane, n-pentane, iso-pentane, n-octane, methyL cyclopentane, and 2,2-dimethylbutane whereby at least a portion of said inert diluent volatilizes thereby abosrbing at least a portion of the exothermic heat of hydroalkylation; and forms (i) a vapor containing said volatilized inert diluent and (ii) cooled product stream; and withdrawing said vapor containing said volatilized inert diluent.
 16. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen which comprises passing said charge benzene, hydrogen, and an inert diluent in liquid phase through a first hydroalkylating operation at inlet temperature within the hydroalkylation temperature range of 25*C-230*C and at hydroalkylation pressure in the presence of hydroalkylation catalyst thereby forming a partially hydroalkylated product stream; flashing said partially hydroalkylated product stream to a pressure lower than that prevailing at the outlet of said first hydroalkylation operation thereby volatilizing at least a portion of said inert diluent and cooling said partially hydroalkylated product stream to a temperature below that prevailing at the outlet of said first hydroalkylation operation; passing said cooled partially hydroalkylated product stream and hydrogen to a second hydroalkylation operation at inlet temperature within the hydroalkylation temperature range of 25*C-230*C in the presence of hydroalkylation catalyst thereby forming a hydroalkylated product stream; withdrawing said product stream containing said hydroalkylate; and recovering hydroalkylate from said withdrawn product stream.
 17. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen as claimed in claim 16 wherein the pressure in said second hydroalkylation operation is less than the pressure in said first hydroalkylation operation.
 18. The process for hydroalkylating a charge benzene with a hydroalkylating quantity of hydrogen as claimed in claim 16 wherein the pressure in said second hydroalkylation operation is equal to the pressure to which said partially hydroalkylated product stream is flashed upon exiting said first hydroalkylation operation. 